It is well established that variation in heart rate during respiration (respiratory sinus arrhythmia) correlates highly with health risk, and is especially indicative of health outcomes associated with acute heart conditions, where less variability is indicative of increased risk of poor outcome. Decreased HRV is generally an outcome of autonomic nervous system imbalance, specifically excessive sympathetic (activating) emphasis and deficient parasympathetic (deactivating) emphasis. Heart failure correlates highly with sympathetic overdrive and diminished HRV. The authors cite previous work that suggests that this progression toward autonomic imbalance is indicative of the progression in heart failure.

HRV is generally considered to be a measure of autonomic tone and cardiovascular adaptability to varying demand, where “adaptability” is a sign of robustness and lack of adaptability its opposite. Exercise tolerance is similarly a measure of the human organism’s ability to adapt to increased work load, cardio-pulmonary performance underlying both measures.

Heart failure patients receiving a six week course of HRV biofeedback and breath training increased exercise tolerance as compared to a control group which received training in a six week placebo program of quasi-false alpha theta EEG biofeedback that had previously been established not to produce cardiovascular effects. Both the treatment group and the placebo group received equal training once per week for 6 weeks and were requested to practice what they learned at home for 20 minutes each day. The HRV/breath training involved breathing more fully and deeply in such a way as to maximize variation in heart rate which was monitored with an instrument. Participants also used an instrument to monitor their HRV during home training.

Improvement in the treatment group was limited to those participants that demonstrated relatively higher (31% or greater) left ventricle ejection fraction (LVEF), where LVEF is an accepted indicator of heart disease severity, the higher LVEF being indicative of less severity. 50% of treatment group participants with higher LVEF demonstrated statistically significant increases in exercise tolerance. Additionally, participants with higher LVEF demonstrated an upward trending improvement in heart rate variability during the study period. Improvement in both exercise tolerance and HRV were effectively limited to those with less severe heart failure.
While not the first of its type, this is an important study because it focuses on the phenomenon of heart rate variability in its proper physiological context, i.e. as a biological indicator of cardio-vascular-pulmonary-respiratory integrity.

About Stephen Elliott

Stephen is the principle author of The New Science of Breath
and Coherent Breathing: The Definitive Method. He is an avid heart rate variability researcher and the inventor of the “Coherent Breathing” method as well as “Valsalva Wave Pro” – an instrument that monitors the blood wave in the circulatory system produced during resonant breathing (See www.coherence.com and www.valsalvawave.com, respectively).